Mining vehicles utilized in underground mining operations are adapted to accommodate the tight confines of the environment in which the vehicles operate. Narrow passageways, tight turns, low roofs, and small staging or depot areas give rise to vehicles which have low profiles, either shorter wheel bases or articulated frames, and heavily re-enforced operator cages.
Propulsion underground can be accomplished through the use of diesel or electric motors, though battery-driven electric motors provide advantages by reducing emissions and plug or hose residues, as well as reducing the instances of combustion-related accidents. Electric motors are powered by batteries of various chemistry types, and tend to be comprised of cells which are heavy and not easily maneuvered.
In underground mining operations, there are distinct advantages to powering vehicles and related equipment with batteries. These advantages include: reduction of emissions; relative safety; and reduction in combustion-related accidents. As with typical household battery uses, after a certain period of time there will be a need to replace the battery. Battery replacement can be facilitated by being able to drop the battery at a designated staging area and mounting a replacement.
Cells make up the individual batteries. In turn, the batteries are housed in battery boxes which provide a certain ruggedized protection to the batteries while the batteries operate in the mining environment. For those batteries that have microprocessors which monitor battery data or performance routines, it may be required that all, or a portion of, the battery be housed in an explosion proof box. The battery boxes, when mounted to the mining vehicle, are supported by trays or compartments. Replacement of the batteries is neither efficient nor easy. Due to the size and/or weight of the batteries, combined with the tight confines inside the mine, changing batteries in a vehicle can be problematic and time-consuming.
Additionally, the surfaces over which vehicles move during mining operations can be undulating and rough. Travel over these surfaces can cause abrupt shifts or other jarring actions to the batteries being carried by and/or powering the vehicles. These shifts or jarring actions can cause the batteries to become dislodged from the vehicles, which poses significant safety risks and/or ceases supply of electric power to the vehicles.
Some currently available underground mining battery-powered vehicles do not have onboard battery changing systems. Swapping batteries in these machines requires the use of a hoist or other lifting equipment. This causes more machine downtime during the required battery charging or swapping cycles and additional equipment to maintain. Another problem with requiring external lifting rigging for battery removal is that this equipment must be moved as the active mine face advances to keep the battery changing area near the working area.
Using a battery changing system as designed for use on mining scoop vehicles could cause additional problems. Hard rock mines typically have narrower hallway widths than coal mines. Because the vehicle must be able to operate in the confined space of these mines, the overall machine dimensions are limited. The confined spaces of the mine also cause problems when unloading material from the bucket. Therefore, an ejector blade is used to remove material. The problem with other known designs is that the hydraulic cylinder(s) used to operate the ejector blade are difficult to extract for replacement or servicing. Also, arrangement of the cylinder tends to not to reduce the force on the ejector as more force is needed to move the blade at the beginning of the cylinder stroke because the bucket is full of material.